Within the scope of the present application, a tube is defined as an elongated element the length of which is generally substantially larger than its cross-section and which is produced from a substantially inflexible material. Pipes can have any open or closed cross-sectional shape, wherein round and rectangular pipes are the most common pipes. Pipe-shaped elements that are produced from pipes by laser cutting are designated as pipe parts within the scope of the present application.
FIG. 1 shows a processing machine 1 for laser cutting of pipes 2 known as “TruLaser Tube,” which is designated as a laser cutting machine and is designed for processing pipes having any cross-sectional shape. The illustrated laser cutting machine 1 comprises a supply device 3 for lateral supply of a pipe 2 to be cut to the laser cutting machine 1, a processing device 4 for laser cutting of pipe parts from the pipe 2 and a discharge device 5 for discharging the cut pipe parts out of the laser cutting machine 1. All essential functions of the laser cutting machine 1 are controlled by means of a numerical control device 6.
The supply device 3 comprises a rotating and feeding means 7 that serves as workpiece moving means, and a machine bed 8 with guiding rails 9 and a push-through means 10. The rotating and feeding means 7 is driven by a motor and can be moved in the feed direction 11 on the guiding rails 9. On the side facing a pipe 2 to be fed, the rotating and feeding means 7 has a clamping means 12 that is controlled to be rotatable in the direction of an axis of rotation 13 and surrounds the supplied pipe 2 from the outside to stationarily clamp it. The supplied pipe 2 is supported by a workpiece support 14 integrated in the machine bed 8. The pipe 2 is guided through the push-through means 10 in the area of the processing device 4. The push-through means 10 is designed in such a fashion that the clamped pipe 2 is guided in the feed direction 11 and is not stationarily clamped. The pipe 2 can be rotated about the axis of rotation 13 in the push-through means 10.
The processing device 4 comprises a laser beam source 15 for generating a laser beam 16, a processing head 17 and a beam guidance 18 that guides the laser beam 16 from the laser beam source 15 to the processing head 17. The laser beam 16 exits the processing head 17 and is focused on the outer peripheral surface of the clamped pipe 2. The discharge device 5 is provided on the side of the push-through means 10 facing away from the machine bed 8, and discharges the pipe parts cut from the pipe 2 and the residual pipe out of the laser cutting machine 1.
In order to increase the productivity of the laser cutting machine 1, the laser cutting machine 1 of FIG. 1 has a loading device 19 as automation component with which a pipe 2 is automatically transported into a transfer position 86 (FIG. 3) and transferred to the supply device 3 of the laser cutting machine 1. The machine arrangement of laser cutting machine 1 and loading device 19 is called flexible manufacturing cell 20 (abbreviated as FMC).
When the pipe 2 supplied via the loading device 19 is located in the transfer position 86, the rotating and feeding means 7 is initially in an initial position remote from the processing head. For processing a pipe, the rotating and feeding means 7 moves out of its position with opened clamping means 12 towards the supplied pipe 2 until the end of the pipe 2 facing away from the processing head 17 comes to rest within the clamping means 12. The clamping means 12 is closed and the pipe 2 is thereby stationarily clamped on the rotating and feeding means 7. The rotating and feeding means 7 and the pipe 2 move together towards the processing head 17. The end of the pipe 2 facing the processing head 17 thereby initially enters the push-through means 10 and is moved in the feed direction 11 through the push-through means 10, wherein the pipe 2 can be rotated about the axis of rotation 13 in the push-through means 10. The pipe 2 is delivered to the desired processing position 92 relative to the processing head 17 through movement of the rotating and feeding means 7 in the feed direction 11.
Processing machines are controlled by means of numerical controls that are also called NC controls, wherein NC is the abbreviation of the English term “Numerical Control.” Since the early 1970s, permanently wired NC controls have been replaced by computer-controlled NC controls that are called CNC controls (Computerized Numerical Control). Modern NC controls are exclusively based on microprocessor technology, for which reason the terms NC control and CNC control are practically used synonymously. One advantage of NC controls on the basis of microprocessor technology is that uniform hardware components that are available in large quantities can be adjusted to special processing machines and production tasks by implementing different software components. The current state of modern NC controls is provided e.g. in the textbook by Manfred Weck, Werkzeugmaschinen Fertigungssysteme, volume 4 “Automatisierung von Maschinen and Anlagen” (automation of machines and systems), Springer-Verlag.
NC controls are generally divided into three control units:                MMC control unit (Man Machine Communication) as data input and visualization unit,        adjustment control unit as central control unit that is also referred to as SPS or PLC, wherein SPS is the abbreviation of the term “memory programmable control,” in English Programmable Logic Controller, abbreviated as PLC,        NC control unit.        
Data or control commands input via the MMC control unit are decoded in the NC control unit, separated and further processed in accordance with geometrical data, technological data and switching functions. Geometrical data contains e.g. path information about the paths on which the tools and workpieces must be moved (processing head and pipe movement), whereas technological data contains e.g. processing parameters such as feed speed and laser beam power. Switching commands control e.g. tool change, feeding of parts (load pipe) and removing parts (unload pipe part). Switching commands are passed on to the SPS control unit where they are linked with responses from the processing machine and are transformed into control commands for the units to be switched in accordance with the gradually processed control program. The geometrical and technological data generates corresponding commands of axis movement for the processing machine upon request by the NC control unit. The NC and SPS control units transmit the current status of the machine to the MMC control unit for visualization.
The three control units, MMC, SPS and NC control unit were realized in the form of separate processors (multi-processor technology) in the past due to limited processor power. Modern processors are so efficient that even one single processor (so-called single-processor technology) can provide the required power. With NC controls with single-processor technology, the MMC, SPS and NC control units are only separated at the software level today.
For controlling a processing machine, the NC control requires a suitable control program that is also called NC program. Each command to a processing machine is expressed in the form of so-called functions encoded in a DIN code. Basic functions that are used for each processing method are stated in international guidelines, in particular in the DIN standard 66025. The basic functions include movement information to a defined position, geometrical information describing the contour profile of a part (sheet metal part, pipe part) and technological information for the production of the contour (e.g. laser cutting). In addition to the basic functions that are defined in the DIN code, the machine manufacturers develop special NC functions for their processing machines and the associated processing methods. For laser cutting of pipes, the different wall thicknesses require e.g. different piercing methods that can each be accessed via their own NC functions.
For automatic generation of NC programs, machine manufacturers and software companies developed so-called programming systems. Programming systems know the basic and special NC functions and know which technology data is required and which processing rules are applied.
In this way, they can automatically define the processing and generate an NC program. Special NC functions are stored and documented in the programming system such that a programmer can use an NC function without knowing its DIN code. Nowadays, a programmer does not need any classical programming knowledge, his/her expert knowledge rather includes finding the optimum processing parameters and processing strategies.
FIG. 2 shows the numerical control device 6 of the laser cutting machine 1 of FIG. 1 that comprises all hardware and software components that are used to control the laser cutting machine 1 and the manufacturing cell 20.
On the hardware side, the control device 6 comprises an MMC control unit 30 with a control computer 31 that is e.g. designed as an industrial PC, and an operating means 32 having a screen 33 as display unit, and a keyboard 34 as input unit, as well as a machine control panel 35 for manual operation of the laser cutting machine 1 and of the manufacturing cell 20, and an NCU assembly 36 (Numerical Control Unit) with integrated NC control unit 37 and SPS control unit 38. All hardware components of the control device 6 are networked via a bus system (not shown) to which further control components can be connected. The MMC control unit 30 and the NCU assembly 36 with NC and SPS control units 37, 38 are designed in the form of two separate components in this embodiment. In an alternative fashion, the MMC, NC and SPS control units 30, 37, 38 can be designed in the form of three separate components or as one common processor for single-processor technology. The control computer 31 and the NCU assembly 36 can be disposed in a switch cabinet (not shown) associated with the laser cutting machine 1.
On the software side, the control device 6 comprises operating software for controlling the automation components (loading device 19) as well as software modules for job management, tool management and pallet management that are combined as operating software 39 for the manufacturing cell (manufacturing cell operating software, FMC software). Operating software 40 for the laser cutting machine (machine operating software, MMC software), program management 41 for managing the NC programs and, if necessary, further applications such as e.g. a programming system 42 are installed on the control computer 31 in addition to the FMC software 39 for the manufacturing cell.
In order to be able to create an NC program that is called NC parts program in a programming system for a pipe part to be cut, the programmer requires a design drawing of the pipe part that is loaded into the programming system. A pipe part is constructed by means of a construction system 43 (CAD system) or a combined construction and programming system 44 (CAD/CAM system), wherein the abbreviations CAD and CAM stand for Computer Aided Design and Computer Aided Manufacturing. The finished design drawings are stored in a common CAD data storage 46 provided for this purpose in a network 45, which the programmers can access when required.
An NC parts program for laser cutting of a pipe part can be created in two different ways. In the first case, the NC parts program is created during work preparation by means of a programming system and transferred to the control device 6. Previously read-in NC parts programs can be subsequently changed or corrected via the operating means 32. In the second case, the machine operator manually creates the NC parts program on the operating means 32 of the MMC control unit 30. In the embodiment shown in FIG. 2, in addition to the programming system 42, further programming systems are installed in the network 45 on the control computer 31 in the form of a combined construction and programming system 44 (CAD-/CAM system) and a pure programming system 47 (CAM system). The control computer 31 and the programming systems 42, 44, 47 are connected to a CAM data storage 48 that the programmers and machine operators can access. The programmer stores the finished NC parts programs in the CAM data storage 48. The machine operator can access the CAM data storage 48 and import the NC parts programs from the CAM data storage 48 into the program management 41 of the control computer 31. The data transfer of the NC parts programs into the program management 41 can also be realized via a storage medium such as a CD ROM or a USB stick such that it is also possible to import NC parts programs that are not stored in the CAM data storage 48 into the program management 41.
For producing a pipe part on the laser cutting machine 1, the machine operator generates an order table 49, schematically indicated in FIG. 1, in the FMC software 39, in which table a parts order 49a, 49b is created for each pipe part stating the quantity of pipe parts in addition to the program name of the associated NC parts program. During creation, the parts orders 49a, 49b are associated with a status “blocked” or “approved.” Only approved parts orders, i.e. parts orders that have the status “approved” are processed on the laser cutting machine 1. Blocked parts orders, i.e. parts orders that have the status “blocked” cannot be processed and are therefore not taken into consideration in automatic pipe allocation. The FMC software 39 shows the status “active” in the order table 49 when an approved parts order is being processed on the laser cutting machine 1. A parts order that was duly processed shows the status “finished” in the order table 49.
FIG. 3 shows the loading device 19 of the laser cutting machine 1 of FIG. 1. The loading device 19 comprises a bundling recess 80 for receiving pipes 2, a separating means 81 for separating the pipes 2 from the bundle recess 80, a lifting means 82 for lifting a separated pipe and a transfer means 83 with grippers 84 for transferring the pipe 2 to the supply device 3 of the laser cutting machine 1. Since the pipes can differ in length by up to a few centimeters, the loading device 19 moreover includes a measuring means 85 for measuring the length of the pipes. The length must be measured to determine the X position (position in the feed direction 11) of the transfer position 86 of the pipe to the rotating and feeding means 7.
During processing of a pipe on the laser cutting machine 1 or during unloading of the residual pipe, the loading process of the next pipe is prepared. The process “prepare loading” includes the method steps to move a pipe 2 out of the bundle recess 80 via a measuring position 87 into a waiting position 88. The pipes are fed and measured during machining until the waiting position 88 is reached.
Several pipes 2 that are provided for processing on the laser cutting machine 1 are located in the bundle recess 80. The pipes 2 are automatically transferred from the bundle recess 80 to the separating means 81. The separating means 81 of the present embodiment has a first transport section as an accumulation section 89 and a second transport section as a separation section 90. The accumulation section 89 and the separation section 90 consist of motor-driven conveyor chains that extend parallel to each other and cross each other. The pipes 2 disposed on the accumulation section 89 are transferred to the separation section 90. The pipes 2 are pulled apart and thereby separated by increasing the transport speed of the separation section 90 with respect to the accumulation section 89.
The lifting means 82 is provided at the end of the separation section 90 for lifting one single pipe 2 into the measuring position 87 in which the length of the pipe 2 is measured using the measuring means 85. The measurement of the length is performed automatically through movement of a toothed belt drive, provided with a pressure sensor, against an electrically detected switch. The measured value of the pipe length is transferred by the measuring means 85 to the control device 6 of the laser cutting machine 1. The grippers 84 of the transfer means 83 move from a basic position 91 to the measuring position 87, take over the pipe 2 after its length has been measured and move together with the pipe 2 to the waiting position 88 in which they remain until the loading process is approved. As soon as the grippers 84 with the pipe 2 are arranged in the waiting position 88, the process “prepare loading” is terminated.
After approval of the loading process, the grippers 84 move into the transfer position 86 in which the measured pipe is transferred by the grippers 84 to the rotating and feeding means 7. When the pipe 2 is in the transfer position 86, it is clamped by the clamping means 12 of the approaching rotating and feeding means 7. The grippers 84 return to their basic position 91. The loading process is terminated and the message “pipe loading terminated” appears on the screen 33 of the MMC control unit 30.
In the conventional laser cutting machine 1 of FIG. 1, the pipe allocation with several pipe parts to be cut is either created in the associated programming system 42, 44, 47 or in the FMC software 39 of the control computer 31.
The programming system “TruToPs Tube” used by the conventional laser cutting machine “TruLaser Tube” 1 optionally comprises a nesting module “TubeLink” for optimizing the allocation of a pipe with several pipe parts to be cut. FIG. 4 shows a flow chart of the individual method steps of the method known from TubeLink for optimizing the pipe allocation. In a first step S1, the programmer determines the nesting options, wherein he/she specifies the minimum pipe length of the pipes to be cut, the distance between the pipe parts and the length of the pipe piece that cannot be processed in the dead area of the clamping means 12 as “minimum residual length.” In a second step S2, the programmer creates a new production package or opens an existing one and includes the NC parts programs of the pipe parts to be nested in the opened production package in a third step S3. In a fourth step S4, it is checked whether the production package contains all desired NC parts programs. When the result of the test of step S4 is negative (N), the method is continued with step S3 and a further NC parts program is included in the production package. When the result of the test of step S4 is positive (J), it is examined in a fifth step S5 whether the NC parts programs and therefore the pipe parts are arranged in the desired order. The pipe parts to be nested are disposed on the pipe in the same sequence as recorded in the production package. When the result of the test of step S5 is negative (N), the programmer changes in a sixth step S6 the order of the pipe parts in the production package through re-sorting of the NC parts programs. When the result of the test of FIG. 5 is positive (J) or after step S6, nesting of the pipe part with respect to the previous pipe part is calculated in a seventh step S7. Nesting is defined by displacement of the pipe part in the feed direction 11 (X-offset) and rotation about the axis of rotation 13 (A-offset). In an eighth step S8, it is checked whether the pipe part shall be produced in a quantity larger than 1. When the result of the test of step S8 is positive (J), nesting of the pipe part with respect to the same pipe part is calculated in a ninth step S9. When the result of the test of step S8 is negative (N) or subsequent to step S9, all nesting results from step S7 and, if necessary, of step S9 are stored in a tenth step S10. In an eleventh step S11, it is checked whether a further pipe part is arranged behind the present pipe part. When the result of the test of step S11 is positive (J), the method is continued with step S7 and nesting of the further pipe part with respect to the previous pipe part is calculated. When the result of the test of step S11 is negative (N), the production package is stored as complete pipe allocation in a twelfth step S12. After step S12, the conventional method for optimizing the pipe allocation is terminated.
In an alternative fashion, the pipe allocation of the conventional laser cutting machine “TruLaser Tube” 1 is performed after creating an order table 49 by means of the FMC software 39. The order in which the pipe parts to be cut are arranged on the pipe is determined by one of four allocation types: “fixed allocation,” “endless processing,” “endless processing with filler part” and “longest pipe part at first,” wherein pipe orders for the allocation type “fixed allocation” are manually created by the machine operator and for the other allocation types they are automatically created by the FMC software 39. For the allocation type “fixed allocation,” NC parts programs or pipe parts are manually moved from the program management 41 to the pipe and created as a pipe order and stored. The pipe order is successively processed until the stated quantity of pipe parts has been reached. This type of allocation is mainly suited to produce pipe parts in assemblies. For the allocation type “endless processing,” all parts orders with the status “approved” are used in accordance with their sequence numbers for automatic pipe allocation, and are disposed one after the other on the pipe. Parts orders with the status “blocked” are blocked for pipe allocation and are not taken into consideration in automatic pipe allocation. As soon as the overall length of the pipe has been exceeded, the last pipe part is removed and the sequence of the pipe parts is stored in the form of a pipe order. The number of pipe orders that are created corresponds to the number that is required in order to process all parts orders with the status “approved.” For the allocation type “endless processing with filler part,” the pipe allocation is initially performed analogously to “endless processing.” In order to improve the utilization of the pipe, the parts orders are searched for short pipe parts. These short pipe parts are moved as filler parts into the still usable areas on the pipe that are generated as residual pipes in the allocation type “endless processing” when the parts orders are moved to the pipe exclusively in accordance with their sequence numbers. For the allocation type “longest pipe part at first,” all parts orders with the status “approved” that are sorted according to the pipe part length are used for automatic pipe allocation. The pipe allocation starts with the longest pipe part arranged next to one another until the required quantity has been achieved or the overall length of the pipe has been exceeded. When the quantity of longest pipe parts has been reached, the next shorter pipe part is disposed on the pipe until the required quantity has been achieved or the overall length of the pipe has been exceeded.
The conventional nesting module “TubeLink” optimizes nesting of two pipe parts disposed next to one another on the pipe. With each of the four types of allocation, the pipe parts are arranged in accordance with the so-called rectangular allocation, wherein the pipe parts are shown as rectangles in the unrolling state, wherein the sides of the rectangle are determined by the outer points of the initial and final geometries.